Many boating people have experienced hitting bottom, and even getting stuck on the water from running aground. Great care must always be taken when negotiating shallow waters. Using conventional propulsion systems (such as outboard motors) in shallow waters can be problematic, as these systems can effectively add to the draft of the boat so that opportunities for running aground are heightened.
Trolling motors are generally utilized in low water, and typically when the main engines are off. These motors can provide quick and precise bursts of speed when fishing, so that the fishermen can easily and quickly follow a fish. It has been known to provide such trolling motors on the trim tabs extending from the stem of the boat. One such type of trolling motor is described in U.S. Pat. No. 5,704,308, issued to Anderson on Jan. 6, 1998, and incorporated by reference herein. The '308 patent discloses a system for propulsion in shallow waters employing a trolling motor attached to an upper surface of a conventional trim tab or afterplane. Trim tabs are commonly found on motorboats as long as sixty feet in length as a means for avoiding unnecessary upward travel of the bow during hard acceleration.
Currently, a number of types of trim tab motors are being manufactured. A typical unit, manufactured by Lenco Marine Inc. of Stuart, Fla., requires a minimum of 18 inches of water to work properly. Alternatively, Minn Kota of Mankato, Minn. offers conventional trolling motors having bendable shafts made of composite materials that are designed to flex when hitting bottom. However, both types of systems are often ineffective when called upon to propel a boat after it has hit bottom.
One reason that such systems have proved ineffective is that it is difficult to generate sufficient thrust when motors and propellers are located in close proximity to the rear transom of a boat. Water directly behind a moving boat is usually aerated, which means that it includes air bubbles. Propellers operating in water that is aerated are substantially less efficient and generate substantially less thrust.
Accordingly, it would be desirable to have an efficient propulsion mechanism mountable at the rear of a boat that provides sufficient thrust to propel a boat even when it has bottomed.